What is happening beyond the Irrawaddy shelf break? Insights from new 3D seismic on the delta slope in the northern East Andaman Basin.

Abstract

Several factors have contributed to the deposition of a very thick Neogene clastic sedimentary succession sourced by the Irrawaddy River and its distributaries extending from the Hukawng to the offshore Moattama: 1. Oligocene – Early Miocene back arc extension and thermal subsidence creating a N-S “trough” extending along the present day East Andaman Basin, under the Moattama Basin and probably some way northwards onshore. 2. Uplift of the Indo-Burman range to the West, combined with the Sunda reliefs to the East created an axial distributary system capturing sediment inputs and feeding the main North-South basin. 3. Significant uplift and erosion related to the Indian collision has made available huge amounts of sediments that have thus continually filled the available accommodation such that the overall system prograded very rapidly to the South. This phenomonom has been amplified by the continued uplift of onshore basins that has “cannibalized” older sediments. The present day shelf edge (and maximum point of advance) of this enormous system sits just to the North of Total’s operated Yetagun West Block (YWB), itself nestled between the Alcock and Tanintharyi basement paleo-highs. The block is therefore located at the confluence for Low Stand deep water clastic turbiditic systems being shed from the advancing delta system and into the East Andaman Basin from the Miocene onwards. During the Feb. 2017 AAPG Yangon conference, Total had presented 2D seismic data from the Block highlighting a number of canyons at sea bed and stacked large scale Plio-Pleistocene erosive / constructive channel levee complexes extending into the Andaman Sea abyssal plain to the South. Basin and depositional geometry suggests that Middle and Upper Miocene deposits would contain more distal turbiditic systems deposited at toe of slope or beyond. With the belief that the necessary components of a functioning Petroleum System were present, Total has acquired in 2018, a large 3D survey covering most of the Block to track these reservoir units and identify where they are related to structural and stratigraphic closures conducive to hydrocarbon accumulations. Total will present the initial results from this new 3D (not available at the time of writing), focusing on the interpretation of the depositional systems imaged, placing the whole in the proper structural and stratigraphic context.

AAPG Datapages/Search and Discovery Article #90336 ©2018 AAPG Asia Pacific Region, The 4th AAPG/EAGE/MGS Myanmar Oil and Gas Conference, Myanmar: A Global Oil and Gas Hotspot: Unleashing the Petroleum Systems Potential, Yangon, Myanmar, November 13-15, 2018